Shale oil eduction process



Oct. 16, 1962 R. F.Dr-:ER1NG ETAL 3,058,904

SHALE OIL EDUCTION PROCESS Filed April 26, 1960 l l "2; I

tates attent hace 3,5%,94 Patented st. 16, 1962 3,058,904 SHALE UIL EDUCTN PROCESS Roland F. Eeering, Brea, and Glenn E. Irish, Fullerton, Calif., assignors to Union @il Company of California, Los Angeles, Calif., a corporation of California Filed Apr. 26, 1969, Ser. No. 24,802 1S Claims. (Cl. 20S-1l) This invention relates generally to a process for the continuous treatment of oil-containing or oil-producing solids for the extraction of gas and liquid products therefrom. More particularly, the invention relates to a new and improved process for the retorting of oil shale to recover optimum hydrocarbon oil and gas values therefrom.

The essential features of our invention entail a novel hot gas recirculation retorting and its use with combustion retorting in an integrated eduction process. This process comprises the advantageous combination of the best features of combustion retorting and hot gas recirculation retorting, wherein a portion of the hot gas circulation retort product gas is recycled as the eduction fluid therein, and lthis recycle gas stream is indirectly heated by hot ue gases from combustion of the low B.t.u. waste product gas from combustion retorting.

Typical retorting processes for treating oil shales involve the downward passage of shale as a moving bed by gravity through a vertical kiln. During this passage the shale solids are heated to eduction temperatures by direct or indirect means. These processes are thermally ineilicient because the heat employed to raise the shale to eduction temperatures is largely lost from the process in producing hot spent shale and in cooling and condensing the product vapors. To avoid the large fuel consumption otherwise required, most of these processes introduce air or other oxygen-containing gas into the bottom of the kiln to burn the carbonaceous residue from the spent shale. This generates hot flue gases lfor heating the shale. However, difficulties are encountered with the fusion of the spent shale due to this burning and frequently the fused or partially fused shale plugs the air inlet. Since the hydrocarbon product is usually removed as a Vapor or mist at the top of a countercurrent solids downow kiln, extensive cooling and condensing facilities are required for the product streams. However, most oil shale is located in areas where cooling water is extremely scarce, thus making these solids downow processes impractical. In other similar processes the oil is condensed on the shale forming a mist and is carried out by the gas stream. However, this also causes continual operating difhculty and product loss because of runback of the liquid oil into the hot kiln where it is decomposed or otherwise lost.

Shale retorting processes which have successfully eliminated the large fuel and condensing water requirement-s, and the difficulties resulting from the relluxing of oil in solids-downtlow retorting, utilize an upflow of shale solids and a downilow of flue gas, e.g., the combustion retort of Berg (see U.S. Patents Nos. 2,501,153, 2,640,014 and 2,640,019). In this type of retort the oil shale is received from storage into a hopper where it passes yby gravity into a vertically acting piston feeder located below the kiln proper. This solids feeder passes the shale upwardly successively through a perforated Huid-solids disengaging zone, a shale preheating zone, a shale oil eduction zone, a spent shale burning zone, and a shale ash zone from which it is expelled for disposal. Air or other oxygencontaining gas enters the ash zone at the top of the kiln and flows downwardly where it is rst preheated in cooling the hot shale ash. The heated air then flows into the burning zone where the carbonaceous residue on the spent shale is combusted forming hot flue gas and hot shale ash. This hot flue gas then continues downwardly into the eduction zone where it heats the raw shale to eduction temperatures. Hydrocarbon oils and gases are ev-olved in the eduction zone forming spent carbonaceous shale and a mixed fluid phase comprising flue gas together with liquid and vapor educted products. The entire fluid phase passes ydownwardly through the preheating Zone in direct contact with the cool raw shale and is cooled, thereby condensing shale oil and preheating the raw shale near the bottom of the kiln. 'Bhe liquid and gaseous products, drawn off at the perforated disengaging zone, are separated from the upwardly moving shale. This combustion retorting process supplies its own fuel in the form of carbonaceous spent shale and cools and partially condenses its own product in preheating, the cool raw shale. Thus, two of the more significant advantages of the solids upilow combustion retort are the highly eilicient extraction of the fuel -value from the oil shale and the minimum retorting utility requirements.

Despite its superiority over other oil shale eduction methods, several inherent features of the solids upow combustion -retorting process are occasionally bothersome. Since both the eduction and the combustion are carried on in the same vessel, it is diicult to vary the conditions of the two steps independently. Thus, ternperature, ow rate, and composition of the combustion gas largely `determine the eduction conditions. The process derives its heat from the burning of a solid hydrocarbonaceous residue on the educted or retorted shale solids by contacting it with an oxygen-containing gas. The required burning temperatures are in the range of about 1,90(l F. to about 2,500 F. inside the kiln in order to maintain the oxidation reactions at suflicient rates. With some oil-producing solids, speeiiically Colorado oil shale, as much as 30 percent to 60 percent of the heat generated by combustion is consumed in uselessly decomposing the mineral Vcarbonates, e.g., calcium carbonate to calcium oxide (lime) and carbon dioxide. These high burning temperatures also result in incipient vfusion or slagging of the shale ash causing the formation of clinkers or partially sintered agglomerates which adversely effect the upilow of shale as well as the downlow of flue gas through the retort.

An additional problem centers around the presence in the system of oxygen required to support the combustion of the ca-rbonaceous residue on the spent shale. A part of this oxygen unavoidably reacts with educted shale oil to form partially oxidized materials which apparently render the liquid portion of the product unstable with resulting fouling of processing apparatus and formation of gums, sludges, etc. A `further problem arises in the disposal of the tremendous quantities of low B.t.u. waste product gas which result from combustion retorting. Combustion retorting product gas is not a particularly v marketable fuel a shale oil eduction zone.V

- liquids, the bottom entry location of the fresh shale feed, kand an about 600 F. and about 1,200 @tween about 800 F. and 1,000

Vera'ble as liquid products.

It is, therefore, an object of this invention provide an improved oil shale retorting process which successfully overcomes these and other problems and which achieves Vhigh oil recovery, yields Ia high B.t.u. shale product gas,

minimizes degradation of the liquid product, and pro- Vduces an oil product of substantially increased stability and quality with reduced-sludge and gum forming ten- 4 dencies.

A more particular object is to provide an integr-ated retorting process in which the highly efcient extraction of fuel values from oil shale found in combustion retorting is combined with the high quality shale'oil and product gas of =a novel recycle gas retort -to yield a higher oil equivalent than can be realized in present retorting processes. Y

We have now found that the foregoing objects and their attendant advantages can be realized in an integrated oil shale retorting process wherein solids-upo-w Vcombustion retorting is integrated with hot gas eduction in Y a solids-upflow, fluid-downow retort in which eduction I is effected without combustion by recirculating anV externally heated portion of the rich product gas to the retort.

More particularly, the unique recycle gas retorting of this invention comprises a substantially continuous up- Ward feed of coarse oil shale particles of upV to about 6 inches, preferably in the size range of about 1/8 inch to about 2 inches, in `a Vertical retort, the kiln section of which typically has a horizontally enlarging area with increase in elevation. VThe retort is enclosed so as to exclude 'air or yany oxygen-containing gas from the interior.

Shale is fed typically by a vertically acting piston feeder located within a feeder case below the kiln, and can be of the form shown inv U.S. Patent No. 2,501,153 to Berg, or any satisfactory form which provides uniform Y. solids upflow vwithin the retort. The solids feeder passes the shale-upwardly successively through a perforated solids-fluid disengaging zone, a shale preheating zone, and Shale particles, having had the optimum oil quantity educted therefrom are removed from the top of the eduction zone. These spent shale particles are found to be substantially unchanged in exterior physical size and conguration throughout this hot recycle gas retorting. Product gases, vapors, and along with eduction uid yare removed just above indirectly heated recycle stream of hot shale product gas is continuously supplied to the top of the enclosed eduction zone.

The hot product recycle eduction gas, preferably at -Y about 1,000 F. to 1,300 F. `and at less than about l,500

F. maximum temperature, pass downwardly into land through the upward ow of shale. This -hot eduction gas e is supplied at a superficial mass velocity of about 100 to about 600 pounds per hour per squarefoot of bed cross-section at the surface of the eduction zone. t These gas ow rates are particularly applicable to oil shale having a Fischer assay range from about 80 gallons per ton to as low as 10 gallons per ton or lower. 'Ihe eduction zone temperature required for the proper eduction of shale in our recycle gas retort is usually between F., and preferably be- F., depending upon the Y 0.10 atmosphere, and

Voil can combine chemically,

and the products desired. The highest temperatures exist at the top of ythe kiln and decrease down through the eduction'zone until the lowest education temperature is found adjacent the shale preheating zone. Shale particles in the eduction zone need not, and preferably do not-exceed about 950 F. These lower temperatures substantially limit carbonate decomposition kwhile still providing complete hydrocarbon eduction. While the eduction zone pressure is usually near atmospheric, the pressures can be either subatmospheric or superatmospheric, -with the pressure at the top of the eduction zone always being higher than the pressure in the lower zones.

The eduction gas, being a recycle shale product gas, contains essentially no free oxygen with which educted nor does it contain many of the conventional diluents found in flue gases such as nitrogen, argon, etc. This product gas, collected with the liquid shale oil product in an accumulation reservoir, is usually withdrawn at a temperature of between about 100 F. yand about 200"y F., preferably at about 100 F., and consists mainly of hydrogen `and light hydrocarbons, e.g., methane, ethane, propane, and the like. A particular feature of this recycled product eduction gas is embodied in its substantially uniform composition, preferably embracing Aan optimum carbon dioxideconcentration. In a preferred embodiment, the recycle gas -is maintained high in carbon dioxide content since this apparently has -a subtype of shale being retorted Vstantial retading effecten mineral carbonate decomposition. The carbon dioxide partial pressure of this preferred eduction gas is not `allowed to drop below about preferably is maintained at a level in the order of 0.15 to 0.30 atmosphere. Any carbon Ydioxide makeup requiredV can be obtained by treatment of a portion of the shale product gas stream, or of other carbon d1oxide-containing streams by conventional means such as di-ethanolamine absorption, hot carbonate absorption,

or other conventional carbon dioxide separation processes.V A particularly preferred source of carbon dioxide in this invention is the low B.t.u. waste product gas stream resulting from combustion retorting.

Excessivey decomposition of carbonates, e.g., magne- Ysium carbonate, calcium carbonate, sodium carbonate and potassium carbonate has been a limiting factor in the utilization of many shale retorting processes. When heated to high temperatures, these m-ineral carbonates bon dioxide partial pressure and heat is consumedV in great such as calcite and dolomite liberate carbon dioxide Vquantities by the endothermic decomposition. Since decreased retorting temperatures decrease decomposition, and increased car- 'also decreases decomposi- Y tion, the relatively low temperature recycle gas retorting process described herein is ideally suited to retorting oil would not be expected to shales with substantial elimination of heat loss from carbonate decomposition. Calcium carbonate (calcite) pose a problem with the low eduction temperatures (around l,000 F.) of this invention, in that Vits decomposition usually starts at about l'1,500 F. However, oil shale is a complex material containing many components, e.g.,

sodium chloride, potasslum chloride, sodium iiuoride,

water, ammonia, and

the like, which catalyze the decomposition of mineral j oarbonates,'such las calcium carbonate, thus lowering the dissociation temperature by several hundred degrees. Thus, the carbon dioxide partial pressure of the eduction gas is advantageously maintained above about 0.10 Iatmosphere (10 percent by volume at atmospheric pressure) which results in eas-ier retorting control, more uniform oil and gas products, and, as a result of reduced heat loss from carbonate decomposition, the use of either a lower temperature eduction fluid or a reduced quantity of recycled eduction gas.

In interrelating the retorting variables of the hot recycle gas eduction as above described, the shale particles in the eduction zone are maintained at a temperature below that at which mineral carbonates, in a carbon dioxide-free atmosphere, undergo substantial decomposition, i.e., less than about forty percent decomposition. This temperature effect is then correlated, in a preferred embodiment, with the carbon dioxide concentration in the eduction gas, which is maintained at a level sufcient to essentially eliminate mineral carbonate decomposition at the particular temperatures, i.e., less than about ten percent decomposition. Thus, at higher eduction zone temperatures, the carbon dioxide concentration is maintained at a relatively high level, while at lower eduction zone temperatures, the carbon dioxide concentration required to suppress decomposition is lower.

Considerable quantities of heat are required in this recycle gas retorting process, often requiring the consumption of a substantial portion of the high B.t.u. gas produced. In typical operations, 60 to 70 percent of the rich product gas is consumed in the heating of the recycle eduction gas. Thus, although the oil product is of much higher quality than is normally obtained in shale retorting, the overall eiciency of fuel value extraction from the oil shale is lower than that found in some retorting processes, e.g., combustion retorting where the heating value of the coke in the spent shale is utilized. The liquid yield from hot recycle gas retorting is appreciably higher than that obtained in combustion retorting and consequently the gas yield is somewhat lower. However, this rich product shale gas from recycle gas retorting is a valuable, high B.t.u., marketable fuel gas, contrasting with the extremely low B.t.u. waste product gas of combustion retorting which has essentially no marketable value because of transport costs.

This invention then, in particular, entails a novel integrated retorting process comprising the combining of uptiow-solids, downtlow-gas combustion retorting with the above-described upiiow-solids, downilow-recycle product gas retorting. That portion of the rich high B.t.u. product gas recycled as the hot eduction fluid for recycle gas retorting is heated by indirect heat exchange with hot flue gases resulting from the burning of the low B.t.u. waste product gas from conventional combustion retorting. Thus, our 4novel integrated retorting process yields a combined fuel product which comprises an increased net production of valuable high B.t.u. product gas, none of which is consumed in the process; no useless production of the low B.t.u. waste gas typical of the combustion retort; and a high yield of a quality shale oil. A particularly preferred embodiment of the invention entails combustion retorting of a portion of the total shale feed just sufficient to produce enough low B.t.u. waste product gas which, when burned, provides the heat required for educting the remaining feed by hot gas circulation retorting. Our integrated eduction process then effectively utilizes the advantages of both conventional combustion retorting and the novel recycle gas retorting. The greater yield of high quality oil from recycle gas retorting, with its concomitant high B.t.u. product gas, supplements the high overall fuel value extraction found in conventional combustion retorting to yield a significantly increased and improved overall fuel oil equivalent. Vital shale oil fuel resources are thus conserved by the production of a maximum of marketable, transportable fuel products from each ton of raw shale.

The improved process of our invention can best be understood With reference to the accompanying drawing which forms a part of this application and the subsequent description thereof. The illustration is a schematic diagram of one example of our novel shale oil eduction process. For simplicity and ease of understanding, `the conventional associated equipment such as liquid oil pumping means, ow controlling means, shale scraper means, solids pumping means, valves, pumps, recycle lines, heat exchangers and the like have for the most part not been illustrated in the drawing since conventional apparatus can be used which forms no part of the invention.

Referring now more particularly to the drawing, the process of the present invention is described in terms of a specific example as applied to the retorting of Colorado oil shale of 0 to 6 inches in average size at a total rate of about 18,150 tons per day to produce a high quality shale oil and a high B.t.u. shale gas. The major apparatus consists essentially of eight parallel recycle gas retorts (one shown), three parallel combustion retorts (one shown), and a fired heater.

Each recycle gas retort has essentially three parts; namely, an upper heat 'treating or eduction kiln 10, an intermediate perforate disengaging section 12, and la lower reciprocating piston shale feeder contained within feeder housing 14. Shale feeder housing 14 contains a vertically reciprocating feeder piston which is contained within an oscillating feeder cylinder, not shown. The feeder cylinder oscillates in a vertical plane between a vertical feeding position, in which it is .aligned with the vertical axis of kiln 10 and disengaging section 12, ,and an inclinded feeder charging position in which the feeder cylinder is inclined from the Vertical and aligned with the lower outlet opening of shale feed hopper 16. The feeder piston and feeder cylinder are separately oscillated hydraulically so that raw shale is drawn into the feeder cylinder from feed hopper 16. The feeder cylinder oscillates into the vertical position, the feeder piston forces the charge of fresh shale upwardly into disengaging section 12 and kiln 10, displacing shale above it upwardly and `displacing spent shale from the top of the kiln. The feeder cylinder then oscillates into the inclined position: to accepta fresh shale charge completing the feeder cycle. This cycle is repeated, thereby continuously feeding fresh shale at the bottom of the structure and displacing hot spent shale from the top. In this way the shaleis passed upwardly through the retort countercurrently to the hot eduction gases subsequently described.

The raw shale feed is introduced at a .rate of about 1,650 tons per `day to each of the eight gas recycle retorts (one shown) through line 18 into shale hopper 16 from which it is fed, as previously described, upwardly through the retort. The shale moves successively upward through a solids-fluid disengaging zone, a raw shale preheating zone, and a shale eduction zone. Surrounding the perforated disengaging section 12 is a collection manifold 20 which constitutes a reservoir for the product oils and gases. During the retorting in kiln 10 the shale is gradually heated to retorting temperatures. The organic matter, commonly termed kerogen, decomposes Iat these temperatures to produce shale oil gases and vapors. 'These educted hydrocarbons move downwardly in the eduction gas flow and `are cooled and condensed by direct contact with the upwardly moving cold fresh shale. The cooled gases and condensed vapors collect in manifold 2G from which they are withdrawn. The liquid oil product lls feeder case 14 which prevents air from entering the retort through shale feed hopper 16.

The liquid portion of the educted product is removed from manifold 20 through line 22 at a temperature of about F. The rich shale gas product of the retorting operation is removed from manifold 20 through line 2'4 at a temperature of about 120 yF. and is introduced into one or more mist and entrainment separators, such as cyclone 26. Here the -gas is freed of residual traces of oil product and the oil is withdrawn from cyclone 26 through line 28 and combined with the larger portion of oil product flowing through line 22.. The mist and entrainment separator can comprise either a cyclone separator, an oil wash such as in an oil absorber, an electrostatic precipitator, or any other suitable separator or combinations thereof for removing finely divided liquid particles from a gas stream.

The oil free retort gas is withdrawn from separator 26 via line Sil by means of blower 32. This maintains and disengaging zone 12 and maintains the lower portion Yof the retort under a slightly subatmospheric pressure. A

net production of about 1,730 M s.c.f./ d. (standard cubic Vfeet per day) of dry shale product gas from each of the eight recycle gas retorts is removed via the blower discharge Vthrough line 42 at a rate controlled by valve 44. This high B.t.u. (986 VB.t.u./cu. ft.) shale product gas streamfrom line 42 has the lfollowing approximate composition.

TABLE 1 Rich Shale Gas Product Mol percent (dry basis) fThe recycled portion of the rich shale product rgas (about 28,300 M s.c.f./d. for each of the eight recycle gas ren torts) is passed from the blower discharge into red heater 36 for heating to eduction temperatures.Y

Y'Ihe car-bon dioxide partial pressure of the recycle gas entering fired heater 36 in this modification is maintained at a Vlevel of at least about 0.10 atmosphere, preferably not above about 0.30 atmosphere, by the introduction, as required, of a carbon dioxide rich stream through line 100 into line 34 at a rate controlled by valve 102. However, this high carbon dioxide partial pressure is not required -for operability and the shale, product gasgcan be used without alteration as the recycled eduction uid.

.Alternatively, carbon dioxide can be fed into line 34 from other process streams, as hereinafter described, via line i434 at a rate controlled by valve v103. Carbon dioxide can also be introduced tothe recycle gas system, if desirable, after the recycle gas has been heated by injecting these carbon dioxide rich makeup streams into line 40. The recycle gas introducing through line34 passes Vthrough recycle gas heating coil 38 and is thence passed through hot recycle gas line 40 into the top of the recycle gas retort at substantially amospheric pressure. The preheating temperatures and gas quantities are controlled so that the recycled eduction gas from fired heater 36 is at a temperature of about l,l50 R as it entersthe recycle gas retort. y

This hot recycle gas ows downwardly through kiln countercurrently to the upwardly moving shale. Here the shale is heated to a retorting temperature of about 950 F., and hydrocarbon gases and vapors are retorted from the shale solids. This retorting normally occurs in the upper half of kiln 10. The educted oils and gases continue downwardly through the. eductionV zone and then through the shale preheating Vzone countercurrent to the rising fresh shale, thus heating the shale solids, cooling the eduction gas, and partiallycondensing the educted products. Since the gases and liquids contact the solids directly, a highly efficient interchange of heat is effected in which the gases are cooled and'additional liquids are condensed as well as subcooling the liquid products previously condensed. This produces the cooled product gas and condensed oils previously referred to Y which collect in manifold 20. 'lln' this direct contact the upwardly rising raw oil shale is preheated in the shale preheating zone to temperatures as high as 300 P.

" to 600 F. at which temperature they enter the eduction zone. Y

- lower outlet opening shale ash from the top,

At the top of kiln'10, spent Vshale accumulates and is Ydischarged into enclosed spent shale hopper 46 by means of rotating or reciprocating Scrapers or plows, not shown, mounted in the top of hopper 46. The educted shale discharges at a temperature Yof about 950 P from spent shale hopper 46 through line '48 and is removed to suitable disposal facilities by means of spent shale conveyor -50 at the rate of about 1,350 tons per day for each recycle gas retort. To prevent the uncontrolled entrance Vfof air into the enclosed recycle gas retort system, steam or other seal gas is introduced through line 52 at a rate controlled by valve 54 into the lower portion of spent shale hopper 46. A rotary airlock or an equivalent device canalso be used at the ash outlet to prevent air introduction.

Simultaneous retorting of the remainder of the raw shale feed is carried out in three parallel combustion retorts, one of which is shown and described. The combustion retort, similar structurally to the aforementioned recycle gas retort, also comprises essentially three main parts; namely, an upper heat treating or eduction kiln 60, an Vintermediate solids-iluid disengaging section 62 and a lower reciprocating piston shale feeder, not shown, contained within feeder housing `64. Shale feeder housing 64 contains a vertically reciprocating feeder piston which is contained within an oscillating feeder cylinder. The feeder oscillates in a Vertical plane between a vertical feeding position, in which it s aligned with the vertical axis of kiln and disengaging section 62, and an inclined feeder charging position in which the feeder cylinder is inclined from the vertical and aligned with the of shale feed hopper 66. The feeder piston and the feeder cylinder are separately oscillated hydraulically so that raw shale is drawn into feed hopper 66, the feeder cylinder oscillates into the vertical position, the feeder piston forces the charge of fresh shale upwardly into disengaging section '62 and kiln 60, displacing solids above it upwardly and displacing and then the feeder cylinder oscillates into the inclined position to accept a new shale charge completing the feeder cycle. In this way the fresh shale is passed upwardly through the combustion retort. Surrounding the perforated disengaging zone 62 is a ,jacket which constitutes a collection manifold for the f shale oils and gases produced during retorting.

' raw shale is then passed, as described above, upwardly suitable shale ash disposal facilities.V conventionally displaced from the top through gas and liquid disengaging section 62 in which the cooled flue and shale gases and the condensed shale oil' are'disengaged from the upwardly moving mass of shale in kiln 60. The upwardly moving shale passes successively through a fresh shale preheating and product cooling and condensing zone, a shale eduction zone, a spent shale combustion zone, and a shale ash cooling and gas preheating zone. The shale Vash is displaced from 'the top of kiln 60 into housing 96. This ash falls by gravity into line 98 atV the bottom of housing 96 and discharges at a temperature of about l,200 'R onto shale ash disposal conveyor 100 from whence it is carried to The shale ash is of the combustion retort by means of Scrapers or plows, not shown, mounted in the top of housing'96. A

In order to support the carbonaceous spent shale combustion, an oxygen-containing gas such as air is introduced through line 92 at a rate controlled by valve 94. Air can also enter via line 98 intohous'ing 96, thus being preheatedrby the hot ash therein. With this gas can of the mixture of shale gas and liue gas produced from f separator 78, hereinafter described. This combustion sustaining gas, air in this case, passes downwardly through gas retort which is flowing the aforementioned zones. In the uppermost or shale ash cooling zone, the air is preheated by direct Contact With the shale ash thereby cooling the ash to a convenient handling temperature. The preheated air then moves downwardly into the spent shale combustion zone where hot ilue gases are generated and the carbonaceous shale is burned forming the shale ash. ln the next lower or eduction zone the hot flue gases educt shale oil and gases from vpreheated fresh shale, forming spent carbonaceous shale and a vapor mixture of shale `oil and gas together with the flue gas. In the next lower or shale preheating zone the fresh shale Vis lpreheated by direct contact with the vapor mixture from the eduction zone thereby cooling and partially condensing it and forming a liquid oil phase, a cooled gas phase and preheated fresh shale. The cooled gas phase continues downwardly with the gravity flow of liquid product. This liquid product fills feeder case 64 thus sealing shale feeder hopper 66 against entry of air.

By means of suction from blower 84 the cooled eduction products separate from the shale solids and pass through the slots in disengaging section 62 into eluent manifold 70 surrounding disengaging section 62. The gas phase flows from manifold 70 into centrifugal separator 76 via line 76. IIt is to be understood that separator 7S can comprise an oil wash such as in an absorber, an electrostatic or ultrasonic treatment, any liquid scrubber to clean up residual dust and oil mists, or other suitable separators. From separator 78 the agglomerated oil phase is removed through line 60 and combined with the liquid product produced through line 72, at a temperature of about 125 F., from product manifold 70. The liquid phase from the combustion retort Withdrawn via line 72 is combined with the liquid phase from the recycle gas retort in line 22 and the mixture passed to suitable storage via the common product oil line 74. For the feed rate of 18,150 tons per day of Colorado oil shale, whose Fischer' assay is 37.5 gallons per ton, the liquid product flow rate through line 7 4 is approximately 14,150 barrels per day of 20.5 APT gravity oil.

The gas phase from separator 78, at a temperature of about 125 F., flows through line'82, blower S4 and line 86 into the combustion chamber of tired heater 36. This product gas from the combustion retorts has the approximate composition shown in Table 2 and a heating value of about 136 B.t.u./ cu. ft. on a dry basis.

TABLE 2 Combustion Retort Shale Gas This low B.t.u. product gas from the three combustion retorts, produced at a total rate of about 85,500 M.s.c.f./ stream day, is burned in sulicient air entering fired heater 36 via line 88 to produce a substantially inert flue gas which is vented to the atmosphere Via stack 90 after heat exchanging with heater tubes 3S. A portion of the gas product from separator 7S can also be recirculated in part to kiln 60 as previously described. This combustion of the-waste shale product gas provides all of the heat required to heat the recycled eduction gas for the recycle through fired heater coil 38.

In one modification of our `process a portion of the product gas leaving centrifugal separator 7S flows to carbon dioxide separator via line 108. In this modification, normally closed valves 106, 116, and v103 are opened. In carbon dioxide separator 110, the combustion retort product gas is separated into two streams. A carbon dioxide depleted fuel gas stream is returned vto the system via line 112 at a rate controlled by valve 116. The fuel gas stream in line 112 has a substantially higher heating value than vthat of the waste product gas from centrifugal separator 78. Thus, in this modification, by combining the rich fuel gas in line 112 with the low Btu. product gas in line 86, the mixture is suiciently enriched so that it becomes possible to utilize very low heating value Waste product gases from Vcombustion retorting that normally could not be burned as a fuel in fired heater 56. A portion of this treated fuel gas stream in line 112 can also be returned to the combustion retort if a partial product gas recycle is desired. A carbon dioxide-rich stream lis withdrawn from carbon dioxide separator 110 viaI line 10ftand is introduced as makeup into line 34 at a rate controlled by valve 103. Valve 102 can then be closed if the 4carbon dioxide malreup from line 104 is sufcient.

The contact time required for substantially complete eduction in either the recycle gas retort or the combustion retort can be as low ias 10 minutes or less, and generally does not exceed 6 hours. Contact times of from about one-half hour to about three hours are normal. The llonger contact times are required where the eduction temperatures are in the lower part of the preferred range and the shale panticles are relatively large. In the practice of the invention as described above, the shale is usually crushed to particles between about 0 andiabout 6 inches, preferably of a size which passes a two-inch mesh sieve and is retained on a one-eighth inch mesh sieve. However, either larger or smaller sizes can be used.

The significant advantages of our integrated retorting process is best illustrated by comparing the integrated combustion-recycle retorting process of the above example with the individual retorting of the same oil shale quantity by conventional combustion retorting alone and recycle gas retorting alone. Table 3, outlining the important differences in these retorting approaches, emphasizes the increased total equivalent oil yield obtained with this embodiment of the process invention.

TABLE 3 Retortmg Comparzson Combus- Integrated Retort Type tion Recycle Combustion- Recycle Number o retorts (1,650 tons] 11 u {3 combustion.

stream day retorts). 8 recycle. Not shale feed to retorts, tous] 18,150 18, 18,150.

stream day. Shale quality, gallons/ton 37. 5 37. 5 37.5 Oil yield, barrels/stream day 12, 100 14, 900 14,150. Net low Btu. gas yield, M s.c.f. 313, 500 0 0.

/s.d. (136 Btu/cu. it.) Net high B .t.u. gas yield, M S.c.f.l 0 4, O75 13,850.

S.d. (9. 6 B.t.u./cu. it.) Marketable fuel oil equivalent of 0 655 2,220.

g)2)s1,)B./s.d. (6.15 MM B.t.u./ Total marketable equivalent oil v12, 100 15, 555 16,370.

yield, b./s.d.

A further comparison, shown in Table 4, illustrates the significant improvement in oil quality such as increased naphtha and decreased residuum content when conventional combustion retorting is replaced by the integrated retorting .technique of our invention.

Y fines consist portion and a coarse Vconsist TABLE 4 Rundown Ozl Combus- Integrated tion Retorting Retorting Oll gravity, kcAPI (water and ash-free basis) 18.6 20.5 Resolution:

N aphtha (Initial-100), vol. percent 5. 3 11.4 Gravity, API 43. 4 42. 7 Gas Oil (40 vis. vol. percen 24. 3 23. 6 Gravity, API 2S. 3 28. 3 Resid., vol. percent 70. 4 65. 0 Gravity, API 14. 1 14. 6 Water, vol. percent 0.5 0.5 Ash, wt. percent 0. 8 0.8 Viscosity:

SSU at 100 F.-- 300 210 SSU at 210 F 49 45 Pour point, F S0 80 Conrarlson carbon, Wt. percent 5. 5.0 Sulfur, Wt. percent 1. 0 0.8 Nitrogen, wt. percent 2.0 2. 0 Ultimate analysis, w" ercent Carbon 84. 2 84. 2 Hydrogen.-- 11. 4 l1. 4 Oxygen 2. 2 1. 6 Gross heating value, B.t.u./1b. (water and ash-free basis) 18, 600 18, 600

A further embodiment of our integrated retorting process comprises segregating the raw shale feed into a portion prior Vto introduction to the retorts. The recycle gas retort, not having a combustion zone with itsV attendant sintering and gas flow problems, is solids consist than the combustion retort. In this modification of our invention, the raw shale feed to the comi the recycle gas retort via bustion retort through line 63 has a particle size, either minimum or average, larger Ithan the raw shale feed to line 18. Thus, for example, the portion fed to line 18 might have a consist of from O to 6- 7 inch particles while lline 68 would introduce a consist of n 2 to 6inch particles.

A further example might feed a consist `of 0 to 3inch particles to line 18, while line 68 would carry a consist of 3 to 6-inch particles.

A still further embodiment of our integrated retorting able to conveniently handle a ner process comprises segregating the raw shale feed into a Y lean consist portion and a rich consist portion prior to feeding these portions, respectively, to the recycle gas retort and the combustion retort. It has been found that as the Fischer assay of a shale feed declines, the percentage oil recovery from combustion retorting correspondingly declines. In contrast, the effect of declining Fischer assay has little, if any, influence on the recovery of oil from shale by recycle gas retorting. Thus, in this modification fof `our invention, the raw shale feed to the combustion retort through line 68 has a higher Fischer assay v value than the shale feed to the recycle gas retort through line 18.

Various other changes and modifications of this invention are apparent from the description of this invention and further modifications will be obvious `to those skilled vin the art. Such modifications and changes are intended to be included within the scope of this invention as defined by the following claims.

We claim:

l. An Vimproved integr-ated retorting process which comprises: educting hydrocarbons from a first body of particulatevoil-producing hydrocarbonaceous solids by contacting said first body of solids with a hot recycleV gas in a non-combustive retorting Zone; collecting oil and a high B.t.u. gas from said non-combustive retorting zone; educting hydrocarbons from a second body of particulate oil-producing hydrocarbonaceous solids by contacting said second body of solids with hot combustion gas in a second.

retorting zone to produce carbonaceous spent solids, said combustion gas being generated by the burning of said carbonaceous spentsolids; Vcollecting oil and a low B.t.u.

gas from said secondrretorting zone; burning at least a portion of said low B.t.u.

gas to produce hot flue gas;

solids feed Y 12Y heating a portion of said high B.t.u. gas to eduction temperature by heat exchange with said hot fiue gas; and passing said heated portion of high B.t.u. gas to said noncombustive retorting Zone as said hot recycle gas.

Y2. A process as dened'in claim 1 wherein said solids comprise oil shale particles of sizes up to about 6 inches in diameter. Y

3. A process as defined in claim `1 wherein said first body of solids is passed upwardly in the form of a dense bed, and said hot recycle gas is passed downwardly, through said non-combustive retorting zone; and wherein said second body of solids is passed upwardly in the form of a dense bed, and said hot combustion gas is passed downwardly, through said second retorting zone.

4. A process for retorting oil-producing hydrocarbonaceous solids which comprises: separating a feed of said solids into a first solids feed portion and a second solids feed portion; passing said first solids feed portion successively through arfirst fluid-solids disengaging zone, a first solids preheating and Vproduct cooling zone, and -a first eduction zone; passing a hot, essentially oxygenfree first eduction uid through saidV first eduction zone and thereby educting liquid and gaseous hydrocarbons from said first solids feed portion; cooling said liquid and gaseous hydrocarbons in said first solids preheating and product cooling Zone thereby obtaining a first gas phase and a first liquid phase; withdrawing said first liquid phase and said first gas phase from said first fluidsolids disengagingY zone; separating said first liquid phase from said first gas phase; heating a portion of said first gas phase to eduction temperature by heat exchange with hot flue gases; passing said heated portion of said first gas phase to said first eduction zone as said hot first eduction fluid; removing spent-solids from said first eduction zone; passing said second solids feed portion successively through a second duid-solids disengaging zone, a second solids preheating and product cooling zone, a second eduction zone, a combustion zone, and an ash cooling zone; passing an oxygen-containing gas .through said ash cooling zone; contacting spent solids in said Y combustion zone with said oxygen-containing gas from said ash cooling zone thereby burning the carbonaceous residue from said spent solids to produce a hot second eduction iiuid and ash solids; contacting said second solids feed portion in said second eduction zone with said second hot eduction uid thereby educting liquid and gaseous hydrocarbons therefrom; cooling said liquid and gaseous hydrocarbons from said second eduction zone in said second solids preheating and product cooling zone thereby obtaining a second gas phase and `a Vsecond liquid phase; separating said second gas phase and said second liquid phase from said second solids feed portion in said second disengaging zone; separating said second liquid phase from said second gas phase; burning at least a portion of said second-gas phase to produce said hot flue gases; `and removing said ash solids from'said ash cooling zone.

5. -A process as defined in claim 4 wherein said solids comprise'oil shale particles of sizes up to about 6 inches in diameter, and wherein said oxygen-containing gas is 6. A process as defined in claim 4 wherein said Vsecond i portion is that portion of the total feed sufficient to provide a sufficient amount of said hot fiue gas to raise the heat content of said first eduction fluid to a Y value just suflicient to educt said first solids feed portion.

7. A process as defined in claim 4 wherein said solids are mineral carbonate-containing oil shales, and wherein said rst solids feed portion in said first eduction zone is maintainedat a temperature below that at which mineral carbonates undergo substantial decomposition.

8. An oil shale retorting process for obtaining the maximum fuel oil equivalent which comprises: separating a raw shale feed 6 inches in diameter comprising particles of up to about into a first feed portion and a sec- 13 passing said first feed portion upwardly bed from a first solids feeder first fluid-solids disengaging ond feed portion; in the form of a dense zone successively through a zone, a first solids preheating and product cooling zone, and a first eduction Zone; passing an essentially oxygenfree hot first eduction fiuid downwardly through said first eduction zone at a temperature suicient to educt oil and gas from said first feed portion; cooling and partially condensing s-aid oil and said gas in said first solids preheating and product cooling Zone thereby obtaining a first gas phase and a first liquid oil phase; removing said first gas phase and said first liquid oil phase from said first disengaging zone; separating said first liquid oil phase from said first gas phase; heating a portion of said first gas phase to eduction temperature by indirect heat exchange with a hot iiue gas; recycling said heated portion of said first gas phase to said first eduction zone as said hot first eduction fluid; removing spent shale from the top of said first eduction zone; passing said second feed portion upwardly in the form of a dense bed from a second solids feeder zone successively through a second fluid-solids disengaging zone, a second solids preheating and product cooling zone, a second eduction zone, a burning zone, and an ash cooling zone; passing an oxygen-containing gas downwardly through said ash cooling zone; contacting spent shale in said combustion zone with said oxygen-containing gas from said ash cooling zone thereby burning the carbonaceous residue on said spent shale to produce shale ash and a hot second eduction fluid; passing said second eduction fluid downwardly through said second eduction zone at a temperature sufficient to educt oil and gas from said second feed portion; cooling and partially condensing said oil and said gas in said second solids preheating and product condensing zone thereby obtaining a second gas phase and a second liquid oil phase; removing said second gas phase and said second liquid oil phase from said second disengaging zone; separating said second liquid oil phase from said second gas phase; burning at least a portion of said second gas phase to produce said hot flue gas; and removing said shale ash from the top of said ash cooling zone.

9. A process as defined in claim 8 wherein said oxygen-containing gas is air.

10. A process as defined in claim 8 wherein said heated portion of said first gas phase recycled to said first eduction zone is at a temperature between about 1,000 F. and about 1,300 F., and said first feed portion in said 14 first eduction zone is maintained at a temperature no greater than about 950 F.

11. A process as defined in claim 8 wherein said first eduction fluid is provided to said first eduction zone at a rate between about and about 600 pounds per hour per square foot of eduction zone top surface, said shale having a Fischer assay range of between about 10 and about 80 gallons of shale oil per ton of raw shale.

12. A process as defined in claim 8 wherein the mean particle diameter of said raw shale feed is between about 1/s inch and about 2 inches.

13. A process as defined in claim 8 wherein said shale contains mineral carbonates, and which comprises the additional step of maintaining a carbon dioxide partial pressure in said first eduction uid sufficient to essentially eliminate mineral carbonate decomposition in said first eduction zone.

14. A process as defined in claim 8 wherein said shale contains mineral carbonates, and which comprises in addition a step 4of -maintaining a carbon dioxide partial pressure in said first eduction fluid at a value in excess of 0.10 atmosphere.

15. A process as defined in claim 8 wherein said shale contains mineral carbonates, and which comprises the additional step of maintaining a carbon dioxide partial pressure in said first eduction fluid at a value between about 0.15 atmosphere and about 0.30 atmosphere.

16. A process as defined in claim 8 wherein said second feed portion is that portion of the total feed sufiicient to provide a suiiicient amount of said flue gas to raise the heat content of said first eduction fluid to a Value just suiicient to educt said first solids feed portion.

17. A process according to claim 13 which comprises, in addition, treating a portion of said second gas phase to separate carbon dioxide therefrom and to produce a rich fuel gas, and recycling at least a part of said separated carbon dioxide with said recycled portion of said first gas phase thereby maintaining said carbon dioxide partial pressure therein.

18. A process according to claim 17 wherein said rich fuel gas is combined with said portion of said second gas phase burned to produce said hot iiue gas.

References Cited in the file of this patent UNITED STATES PATENTS 1,833,155 Danner et al Nov. 24, 1931 2,601,257 Buchan June 24, 1952 2,881,117 Berg et al, Apr. 7, 1959 

1. AN IMPROVED INTEGRATED RETORTING PROCESS WHICH COMPRISES: EDUCTING HYDROCARBONS FROM A FIRST BODY OF PARTICULATE OIL-PRODUCING HYDROCARBONACEOUS SOLIDS BY CONTACTING SAID FIRST BODY OF SOLIDS WITH A HOT RECYCLE GAS IN A NON-COMBUSTIVE RETORTING ZONE; COLLECTING OIL AND A HIGH B.T.U. GAS FROM SAID NON-COMBUSTIVE RETORTING ZONE; EDUCTING HYDROCARBONS FROM A SECOND BODY OF PARTICULATE OIL-PRODUCING HYDROCARBONACEOUS SOLIDS BY CONTACTING SAID SECOND BODY OF SOLIDS WITH HOT COMBUSTION GAS IN A SECOND RETORTING ZONE TO PRODUCE CARBONACEOUS SPENT SOLIDS, SAID COMBUSTION GAS BEING GENERATED BY THE BURNING OF SAID CARBONACEOUS SPENT SOLIDS; COLLECTING OIL AND A LOW B.T.U. GAS FROM SAID SECOND RETORTING ZONE; BURNING AT LEAST A PORTION OF SAID LOW B.T.U GAS TO PRODUCE HOT FLUE GAS; HEATING A PORTION OF SAID HIGH B.T.U. GAS TO EDUCTION TEMPERATURE BY HEAT EXCHANGE WITH SAID HOT FLUE GAS; AND PASSING SAID HEATED PORTION OF HIGH B.TU. GAS TO SAID NONCOMBUSTIVE RETORTING ZONE AS SAID HOT RECYCLE GAS. 